• Journal of Advanced Marine Engineering and Technology
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• v.36 no.4
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• pp.490-496
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• 2012

The main object of this research is to minimize the shock effects which frequently result in fatal damage in offshore wind turbine on impact of barge. The collision between offshore wind turbine and barge is generally a complex problem and it is often impractical to perform rigorous finite element analyses to include all effects and sequences during the collision. On applying the impact force of a barge to the offshore wind turbine, the maximum acceleration, internal energy, and plastic strain are calculated for each load case using the finite element method. A parametric study is conducted with the experimental data in terms of the velocity of barge, thickness of the offshore wind turbine, and thickness and Mooney-Rivlin coefficient of the rubber fender. Through the analysis proposed in this study, it is possible to determine the proper size and material properties of the rubber fender and the optimal moving conditions of barge.

• Transactions of the Korean hydrogen and new energy society
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• v.23 no.2
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• pp.183-190
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• 2012

The research shows the experiment results according to the combustion characteristics and configuration of the linear generator of powerpack for the generating power applying the 2-stroke compact linear engine. The powerpack used in this paper consists of 2-stroke linear engine, linear generator and air compressor parts. For identifying the combustion characteristics and generating power of linear engine, some parameters were varied sucha as electric load, fuel input calorie, spark timing delay and equivalence ratio. Also generating power was confirmed at each operation conditions, when the air gap length of linear generator part was changed as each 1.0 mm and 2.0 mm. During the all operations, intake air was inputted under the wide open throttle. Mass flow rate of air and fuel was changed using mass flow controller, after these were premixed by premixture device, and then premixed gas was supplied directly into each cylinder. As a result, piston frequency and combustion characteristics were different at each conditions according to parameters affecting the combustion such as fuel input calorie, resistive load, spark timing delay and equivalence ratio. Consequently, these had an effect on generating power.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.4
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• pp.42-51
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• 2018

Verticality problem during the installation process in offshore wind turbine substructures could degrade the safety of the whole structures. Therefore, in this paper, the design of vertically adjustable transition piece(T.P.), using a PS anchor and grout of anchor socket in concrete gravity based substructure(G.B.S.), was proposed. T.P. was designed for 5MW offshore wind trubine and can adjust up to $0.5^{\circ}$ in verticality, occurred during installation. The design plan for each members and design procedure for T.P. was proposed. Then based on the proposed design, actual design targeting sea of Jeju-island was carried out. Finally, by use of non-linear 3D Finite Element Analysis(F.E.A.), evaluation of design was performed. As a result of evaluation, by checking load transfer mechanism and stress of T.P, proposed design was considered safe up to $0.5^{\circ}$ of adjustment.

• Journal of the Korean Institute of Intelligent Systems
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• v.23 no.2
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• pp.151-157
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• 2013

This paper proposes an online adaptive fuzzy controller for a wind energy conversion system (WECS) that is intrinsically highly nonlinear plant. In real application, to obtain exact system parameters such as power coefficient, many measuring instruments and off-line implementations are required, which is very difficult to perform. This shortcoming can be avoided by introducing fuzzy system in the controller design in this paper. The proposed adaptive fuzzy control scheme using self-structuring algorithm requires no system parameters to meet control objectives. Even the structure of the fuzzy system is automatically grows on-line, which distinguishes our proposed algorithm over the previously proposed fuzzy control schemes. Combining derivative estimator for wind velocity, the whole closed-loop system is shown to be stable in the sense of Lyapunov.

• Journal of the Korean Institute of Intelligent Systems
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• v.26 no.4
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• pp.286-294
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• 2016

In the initial design stage, the geometry of systems needs to be optimized regarding its performance. However, performance analysis is very time-consuming. Therefore, optimization becomes difficult/impossible problems because we need to evaluate the system performance for alternative design cases. To overcome this problem, many researchers perform prediction of system performance using the approximation model. The response surface method (RSM) is typically used to predict the system performance in the various research fields, but it presents prediction errors for highly nonlinear systems. The major objective of this paper is to propose a proper prediction method for marine system problems. Case studies of marine systems (the substructure of a floating offshore wind turbine considering hydrodynamic performance and bulk carrier bottom stiffened panels considering structure performance) verify that the proposed method is applicable to performance prediction in marine systems.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.8
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• pp.543-556
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• 2016

In this work, an insulated coupling test machine for a 5-MW-class wind turbine was designed and developed, along with the public performance testing of a 3-MW-class wind turbine. The results of the device design, development requirements, functional considerations, structural vibration analysis, and the evaluation of the insulated coupling test machine are presented in this study. For the coupling models, thick fiberglass composite pipe insulation, fabricated by filament winding, was considered. Results of three-dimensional finite element analysis conducted using both solid element and shell element modeling were analyzed and compared, considering the effect of thickness. In addition, results from the nonlinear finite element analysis of multiple leaf springs of the laminated disk pack structure were verified and compared with experimental data.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.35 no.2
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• pp.93-100
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• 2022

The collision behaviors of the tripod and jacket structures, which are considered as support structures for offshore wind towers at the Southwest sea of Korea, were compared by nonlinear dynamic analysis. These structures, designed for the 3 MW capacity of the wind towers, were modeled using shell elements with nonlinear behaviors, and the tower structure including the nacelle, was modeled by beam and mass elements with elastic materials. The mass of the tripod structure was approximately 1.66 times that of the jacket structure. A barge and commercial ship were modeled as the collision vessel. To consider the tidal conditions in the region, the collision levels were varied from -3.5 m to 3.5 m of the mean sea level. In addition, the collision behaviors were evaluated as increasing the minimum collision energy at the collision speed (=2.6 m/s) of each vessel by four times, respectively. Accordingly, the plastic energy dissipation ratios of the vessel were increased as the stiffness of collision region. The deformations in the wind tower occurred from vibration to collapse of conditions. The tripod structure demonstrated more collision resistance than the jacket structure. This is considered to be due to the concentrated centralized rigidity and amount of steel utilized.

• Management & Information Systems Review
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• v.34 no.5
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• pp.71-92
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• 2015

This study analyzes the impact of Corporate Social Responsibility (CSR) activities on financial performances using Bayesian Network. The research tries to overcome the issues of the uniform assumption of a linear function between financial performance and CSR activities in multiple regression analysis widely used in previous studies. It is required to infer a causal relationship between activities of CSR which have an impact on the financial performances. Identifying the relationship would empower the firms to improve their financial performance by informing the decision makers about the different CSR activities that influence the financial performance of the firms. This research proposes General Bayesian Network (GBN) and presents Markov Blanket induced from GBN. It is empirically demonstrated that all the proposals presented in this study are statistically significant by the results of the research conducted by Korean Economic Justice Institute (KEJI) under Citizen's Coalition for Economic Justice (CCEJ) which investigated approximately 200 companies in Korea based on Korean Economic Justice Institute Index (KEJI index) from 2005 to 2011. The Bayesian Network to effectively infer the properties affecting financial performances through the probabilistic causal relationship. Moreover, I found that there is a causal relationship among CSR activities variable; that is Environment protection is related to Customer protection, Employee satisfaction, and firm size; Soundness is related to Total CSR Evaluation Score, Debt-Assets Ratio. Though the what-if analysis, I suggest to the sensitive factor among the explanatory variables.

• Environmental and Resource Economics Review
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• v.15 no.3
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• pp.505-530
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• 2006

For the district heating and cooling business, it is required to install energy-saving facilities using energy from waste and land fill gases such as combined heat and power(CHP). The current issues that this business faces can be summarized as below: which facilities including CHP can be economically introduced and how much of their capacities should be. Most of such issues are clearly related to the optimal plant design of the district heating and cooling business, and the prices of energy services such as heating and cooling energy, and electricity. The purpose of this study is to establish linear program model of least cost function and to practice the empirical test on a assumed district heating and cooling business area. The model could choose the optimal type of energy-producing facilities among various kinds available such as CHP's, absorption chillers, the ice-storage system, etc. CHP with the flexible heat and power ratio is also in the set of available technologies. And the model show us the optimal ration of heat producing facilities between CHP and historical heat only boiler in the service area. Some implications of this study are summarized as below. Firms may utilize this model as a tool for the analysis of their optimal size of the facilities and operation. Also, the government may refer the results to regulate resonable size of business.

• Journal of Korea Entertainment Industry Association
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• v.14 no.7
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• pp.251-262
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• 2020

The purpose of this study is to analyze musical styles emerging in modern musical history from the perspective of integration and deconstruction, and to academically investigate the characteristics contained in each style. The style of musicals can be divided into periods of non-integrity, integration, deconstruction, and convergence. The rise of musical styles and the associated meanings can be studied from the perspective of modernism and postmodernism. In modernism, the energies of 'integration' and 'concentration' form the major trend while in early postmodernism, the powers of 'deconstruction' and 'dispersion' play the main role. Late postmodernism is a dialectic result of both trends in which the philosophy of 'convergence' and 'harmony' operates as the main theme. The principle of integration and deconstruction, which forms the base of musical creation, emerged after the development of the unstable style of non-integrity in the early days of musical. Later, with the advent of Rogers and Hammerstein II, the principle of integration was established for book musicals, emphasizing the linearity of drama, and the principle of deconstruction was born for concept musicals to contain new contents. The 'convergence' found in later musical works turn the theme from non-integrity to integration, and from deconstruction to integration again, which indicates that integration is embracing the concept of deconstruction again in a more advanced sense. Such convergent compromise that constantly influences each other and develops in a better direction can contribute to the development of musical styles.