• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.5
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• pp.363-373
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• 2014

In this study, computational multi-body dynamic analyses for the drivetrain system of a 5 MW class offshore wind turbine have been conducted using efficient equivalent modeling technique based on the design guideline of GL 2010. The present drivetrain system is originally modeled and its related system data is adopted from the NREL 5 MW wind turbine model. Efficient computational method for the drivetrain system dynamics is proposed based on an international guideline for the certification of wind turbine. Structural dynamic behaviors of drivetrain system with blade, hub, shaft, gearbox, supports, brake disk, coupling, and electric generator have been analyzed and the results for natural frequency and equivalent torsional stiffness of the drivetrain system are presented in detail. It is finally shown that the present multi-body dynamic analysis method gives good agreement with the previous results of the 5 MW class wind turbine system.

• Journal of Elementary Mathematics Education in Korea
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• v.11 no.1
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• pp.61-80
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• 2007

Korea and Japan are close countries having a mutual influence on history and have similar cultural and educational circumstances. The purpose of this study was to compare and analyze the textbooks for elementary school mathematics between Korea and Japan. First, it established the theoretical backgrounds through the precedent research comparing the mathematic textbooks between South Korea and North Korea, Korea and India, Yanbian in China, Japan( Fraction part in numeral field. The Plane Figures). Next, it compared and analyzed two countries'(Korea and Japan) textbooks regarding the structural system and concept of units on the basis of the theoretical research. And it included more specific and detail contents in comparison of Korean with Japanese mathematic textbooks focused on the 5, 6th grade.

• Steel and Composite Structures
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• v.35 no.4
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• pp.555-566
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• 2020

This paper aims to present an analytical methodology to investigate influences of nanoscale and surface energy on buckling stability behavior of perforated nanobeam structural element, for the first time. The surface energy effect is exploited to consider the free energy on the surface of nanobeam by using Gurtin-Murdoch surface elasticity theory. Thin and thick beams are considered by using both classical beam of Euler and first order shear deformation of Timoshenko theories, respectively. Equivalent geometrical constant of regularly squared perforated beam are presented in simplified form. Problem formulation of nanostructure beam including surface energies is derived in detail. Explicit analytical solution for nanoscale beams are developed for both beam theories to evaluate the surface stress effects and size-dependent nanoscale on the critical buckling loads. The closed form solution is confirmed and proven by comparing the obtained results with previous works. Parametric studies are achieved to demonstrate impacts of beam filling ratio, the number of hole rows, surface material characteristics, beam slenderness ratio, boundary conditions as well as loading conditions on the non-classical buckling of perforated nanobeams in incidence of surface effects. It is found that, the surface residual stress has more significant effect on the critical buckling loads with the corresponding effect of the surface elasticity. The proposed model can be used as benchmarks in designing, analysis and manufacturing of perforated nanobeams.

• Structural Engineering and Mechanics
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• v.43 no.2
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• pp.239-251
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• 2012

The analysis of laterally loaded piles is generally carried out by idealizing the soil mass as Winkler springs, which is a crude approximation; however this approach gives reasonable results for many practical applications. For more precise analysis, the three- dimensional finite element analysis (FEA) is one of the best alternatives. The FEA uses the modulus of elasticity $E_s$ of soil, which can be determined in the laboratory by conducting suitable laboratory tests on undisturbed soil samples. Because of the different concepts and idealizations in these two approaches, the results are expected to vary significantly. In order to investigate this fact in detail, three-dimensional finite element analyses were carried out using different combinations of soil and pile characteristics. The FE results related to the pile deflections are compared with the closed-form solutions in which the modulus of subgrade reaction $k_s$ is evaluated using the well-known $k_s-E_s$ relationship. In view of the observed discrepancy between the FE results and the closed-form solutions, an improved relationship between the modulus of subgrade reaction and the elastic constants is proposed, so that the solutions from the closed-form equations and the FEA can be closer to each other.

• Special Issue of the Society of Naval Architects of Korea
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• 2005.06a
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• pp.63-68
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• 2005

Optimum design of the big brackets is performed through iterated 3-D FE analyses to meet the permissible limits of stress, which consumes an excessive amount of calculation time. Therefore, this study has been prepared to determine rapidly and accurately an optimum size and scantling of the big brackets at the initial design stage. The generalized slope deflection method (GSDM) based on the span point concept is applied to enhance the efficiency of iterated structural analyses. The accuracy and applicability of the present method is verified by comparing with a detail 3-D FE analysis of web frame structures. As an optimization technique, evolution strategies (ES) are applied using discrete design variables for practical design.

• Special Issue of the Society of Naval Architects of Korea
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• 2007.09a
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• pp.26-31
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• 2007

After CSR is in effect, a matter of concern is how many to increase in terms of weight due to apply it to the ship and what difference it is comparing between existing rule and CSR rule. The concepts of CSR are to make the ship safer, more robust. and the design requirement clearer. Furthermore it pursues longer life of ship in fatigue strength. By reasons of those, most of requirements are stronger than before. Therefore many part of ship should be reinforced and the weight of ship can be increased. Under those circumstances, the builder should make an effort to define the CSR and to find the methods to manage well this situation. In this study, we performed 3D Cargo hold and Fine-mesh F.E analysis and deduced a conclusion and introduced new detail design.

• International Journal of Aerospace System Engineering
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• v.5 no.1
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• pp.1-8
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• 2018

Military rotorcrafts are constantly exposed to risk from bullet impacts because they operate in a battle environment. Because bullet impact damage can be deadly to crews, the fuel tanks of military rotorcraft must be designed taking extreme situations into account. Fuel tank design factors to be considered include the internal fluid pressure, the structural stress on the part impacted, and the kinetic energy of bullet strikes. Verification testing using real objects is the best way to obtain these design data effectively, but this imposes substantial burdens due to the huge cost and necessity for long-term preparation. The use of various numerical simulation tests at an early design stage can reduce the risk of trial-and-error and improve the prediction of performance. The present study was an investigation of the effects of bullet impacts on a fuel tank assembly using numerical simulation based on SPH (smoothed particle hydrodynamics), and conducted using the commercial package, LS-DYNA. The resulting equivalent stress, internal pressure, and kinetic energy of the bullet were examined in detail to evaluate the possible use of this numerical method to obtain configuration design data for the fuel tank assembly.

• Management & Information Systems Review
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• v.32 no.4
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• pp.225-254
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• 2013

This research tries to examine the effect of brand experience in service marketing perspective for generalized application. The analysis was held with customers who recently visited in retail stores by using SPSS18K and Smart PLS 2.0. The study verified the structural equation model hypothesizing the relationship among brand experience, relationship quality, and relationship strength. According to the result of this study, four brand experience factors have positive effect on the relationship quality. In detail, the effect of sensory experience was strongest. Furthermore, the effect of relationship quality on relationship strength also significant as prior researches addressed. The research has several marketing implication on brand experience management and customer relationship management. For service firms, customers' perception of positive brand experience can generate the tangible and intangible performance in the relationship marketing perspectives.

• Journal of Korea Society of Digital Industry and Information Management
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• v.15 no.4
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• pp.213-225
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• 2019

Privacy paradox is a paradoxical behavior that provides personal information even though you are concerned about privacy. Social media users are also often concerned about their personal information exposure. It is even reluctant to describe personal information in profile. However, some users describe their personal information in detail on their profile, provide it freely when others request it, or post their own personal information. The survey was conducted using Google Docs centered on Facebook users. Structural equation model analysis was used for hypothesis testing. As an independent variable, we use personal information infringement experiences. As a mediator, we use privacy indifference, privacy concern, and the relationship with the act of providing personal information. Social media users have become increasingly aware of the fact that they can not distinguish between the real world and online world by strengthening their image and enhancing their image in the process of strengthening ties, sharing lots of information and enjoying themselves through various relationships. Therefore, despite the high degree of privacy indifference and high degree of privacy concern, the phenomenon of privacy paradox is also present in social media.

• Journal of Information Management
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• v.38 no.2
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• pp.127-152
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• 2007

Children seem to be more familiar with getting information from computer and internet than adults, and also it is true that information behavior in the internet has strong influences in the living of the children. When considering this fact, the public library which is the gateway to knowledge should provide a website for children services, allowing to do their life-long learning, read books and access information, without any restrains from time and space. The purpose of this study is to show the importance of public library website, especially for the children, and also to analyze trend of the country and present the solution to the problems. To achieve these goal, the analysis on the websites of the public libraries in Dagu and Gyengbuk area has been conducted. In detail, these were conducted about following criterions: existence of the website, structural system, search service, and contents.